Dachang Sn-polymetallic ore field, Nandan Co., Hechi Prefecture, Guangxi Zhuang Autonomous Region, China

The Dachang tin-polymetallic orefield is developed witin a belt containing 4000 m of sediments ranging fom lower devonian to tertiary in age, intruded by the cretaceous peraluminous Longxianggai granite. The sediments include devonian black shales, limestones and argillaceous limestones, carboniferous and permian limestones and a younger tertiary cover. Mineralization occurs in three forms, namely

(1) - Stratabound ore bodies, containing 60% of the tin resource at Dachang: The stratabound ore is composed of small cross-cutting and bedding plane veins developed within particular stratigraphic intervals. The stratabound bodies can contain up to 30% sulphide, mainly pyrrhotite, sphalerite, arsenopyrite and chalcopyrite with cassiterite. Some of the larger orebodies may have dimensions of up to 1100 x 700 x 15 m. These bodies can contain around 1% Sn and up to 4% Zn.
(2) - Stockworks: Stockworks of 0.5 to 1 cm thickness veins with a density of 10 to 30 veins per metre have low average Zn and Sn contents and occur in limestones.
(3) - Veins: They are found at the top of the deposits and are typically 0.1 to 0.2 m thick and extend for 50 to 200 m along strike and 100 to 300 m vertically and have high Zn (to 7.5%) and Sn (to 2%).

All of the different styles of ore are contained within an upper devonian unit composed of 5 sub-units, namley black siliceous rock, thick striped limestones, thin striped siliceous limestone, small peas limestone and large peas limestone. The orebodies are found adjacent to a major fault which cuts the Longxianggai granite several hundred metres below the ore zones.

Located about 20 km SSE of Nandan and NW of Hechi.

A geological map of the orefield is available at: http://www.hmzmetals.com/images/gaofeng2.pdf

Ref.:
- Tanelli, G., and Lattanzi, P. (1985): The cassiterite-polymetallic sulfide deposits of Dachang (Guangxi, People's Republic of China). Mineralium Deposita 20(2), 102-106.

- Peng, Z., Watanabe, M., Hoshino, K., and Shibata, Y. (1999): Ore mineralogy of tin-polymetallic (Sn-Sb-Fe-Pb-Zn-Cu-Ag) ores in the Dachang tin field, Guangxi, China and their implications for the ore genesis. Neues Jahrbuch für Mineralogie, Abhandlungen 175(2), 125-151.

- Shao-Yong Jiang, Fa Han, Jian-Zhong Shen, and Palmer, M.R. (1999): Chemical and Rb–Sr, Sm–Nd isotopic systematics of tourmaline from the Dachang Sn-polymetallic ore deposit, Guangxi Province, P.R. China. Chemical Geology 157(1/2), 49-67.

- Pašava, J., Kříbek, B., Dobeš, P., Vavřín, I., Žák, K., Fan Delian, Zhang Tao, and Boiron, M.-C. (2003): Tin-polymetallic sulfide deposits in the eastern part of the Dachang tin field (South China) and the role of black shales in their origin. Mineralium Deposita 38(1), 39-66.

- Delian Fan, Tao Zhang, Jie Ye, Pašava, J., Kříbek, B., Dobeš, P., Vavřín, I., and Žák, K. (2004): Geochemistry and origin of tin–polymetallic sulfide deposits hosted by the Devonian black shale series near Dachang, Guangxi, China. Ore Geology Reviews 24(1/2), 103-120.

- Qin Dexian, Tan Shucheng, Fan Zhuguo, Li Yingshu, Chen Aibing, Li Lianju, Liu Guangliang, Dang Yutao, Tong Xiang, Wu Junde, and Li Yuxin (2004): Geotectonic evolution and tin-polymetallic metallogenesis in Gejiu-Dachang area. Acta Mineralogica Sinica 24(2), 117-123.

- Denghong Wang, Huaqin Li, Yuchuan Chen et al. (2005): Discovery of high－REE calcites in the Dachang superlarge tin－polymetallic ore deposit, Nandan, northwestern Guangxi. Geological Bulletin of China 24(2), 176-180.

- K.-D. Zhao, S.-Y. Jiang, P. Ni, H.-F. Ling, and Y.-H. Jiang (2007): Sulfur, lead and helium isotopic compositions of sulfide minerals from the Dachang Sn-polymetallic ore district in South China: implication for ore genesis. Mineralogy and Petrology 89, 251-273.